A gauge ring is a precisely machined measurement device, typically fabricated from steel or similar durable material, which has a specified internal diameter, which diameter is typically independently verified. In the field of the present invention, the gauge ring is used to confirm the dimensional compatibility of various tools and equipment which must pass through restrictions which may be present in an oil or gas well. Such restrictions include the inside diameters of casing, wellheads, open-hole portions of a well, liner hangers, etc. For purposes of the present invention, the downhole tools which must pass through such restrictions specifically include the general class of tools known as stabilizers. This class of tools includes integral blade stabilizers, welded blade stabilizers, replaceable sleeve stabilizers, non-rotating rubber sleeve stabilizers, replaceable wear pad stabilizers, roller reamers and combination reamers/stabilizers.
Gauge rings utilized in the oil industry are normally of two types. Go ring gauges provide a precision tool for comparative gauging based on a fixed limit. With respect to down hole tools, go gauges provide an indication of whether the tool, along its entire length, has a diameter which may safely be run into a wellbore and through any restrictions contained therein. A go ring gauge's dimensions are based on the maximum OD tolerance of the down hole tool being gauged. In comparison, no-go or not-go gauges provide a precision tool for production comparative gauging based on a fixed limit. No-go gauges consist of a fixed limit gauge with a gauging limit based on the minimum or maximum tolerances of the inspected part. With respect to down hole tools, a no-go ring gauge's dimensions are based on the minimum OD tolerance of the tool.
Failure to confirm the compatibility of the dimensions of a downhole tool can have substantial adverse consequences. If the tool is too large, it can become stuck in a reduced diameter section of the well. If the tool is unknowingly undersized, for example a reamer, the well diameter may not be as large as believed by the drilling personnel. This situation can result in the running of tools which are too large for the well diameter, and the sticking of tools and casing in the reduced diameter portion of the well.
In the case of go-ring testing, the common method of verifying whether the diameter of a stabilizer is safe to run is by sliding a steel gauge ring over the entire length of the tool to reach the largest outside diameter section. If the ring slides over the entire length, the tool is safe to run. In this method, the internal diameter of the steel gauge ring is first verified and certified by a third party, such that the actual diameter is known within an accepted tolerance. However, this method has some disadvantages. First, the ring must be slid around much of the length of the stabilizer until reaching the largest diameter sections around the stabilizer blades. This process can be time consuming because the stabilizer will usually be several feet in length, thereby requiring the ring to be lifted around much of the length of the stabilizer before reaching the larger diameter blade sections. It can also be uncomfortable for the person having to bend down and pull the ring up over the blades. Finally, because many of these operations take place directly over the well opening, it is possible for the steel ring gauges to fall downhole. Because of their steel construction, the loss of a ring gauge downhole can cause substantial difficulties, because of the difficulties which may be encountered in trying to drill up the device.